1. Field of Invention
Remediation of target bacteria occurs by application of a mixture of or serial application of bacteriophage isolated by staged culturing and bacteriophage lysing of bacteria in waters containing a multiplicity of target bacteria. The process is particularily effective for sulfur reducing (SRB) and acid producing bacteria (APB).
2. Background
Microbial fouling affects the entire infrastructure of the oil and gas industry, from production wellheads, throughout transmission pipelines, and the refinery. In particular, sulfate-reducing bacteria (SRB) sour and devalue the petroleum product in reservoirs through the evolution of H2S (hydrogen sulfide) gas. Because H2S was both flammable and a potent neurotoxin, elevated levels were responsible for increased overall risks and costs during exploration and production. Chemical biocides were widely applied to combat bacterial related problems. Biocide treatment results in suppression, rather than elimination, of the problem organisms and has the major drawback of being harmful to humans and the environment. Investigation into new approaches of controlling microbial population in the petroleum industry is prudent.
A relatively new method for controlling SRB is by use of bacteriophage, or phage. Phages are natural, bacteriolytic, viral predators of bacteria. Phages are already being used commercially to control bacteria on cattle and food crops. Phage treatments are available overseas for treating human bacterial infections, particularly in chronic wounds and burns. Regulatory hurdles have prohibited medical applications in the US. However, by analogy it might be possible to develop phage based products to control “bacterial infections” of the oilfield and it is conceivable that a mixture of oilfield SRB-specific phage could be injected at the head of a pipeline or into a reservoir to control SRB associated corrosion and souring.
However, in some trials of oil and gas field waters containing a plethora of SRB varieties, treatment with phage has been found short lived, with bacterial levels being reduced for a short period of time and then recovering. Recovery of total bacterial levels has been found to be due to the appearance of resistant varieties of the original host strain as well as due to the proliferation of minority bacterial strain following the elimination of the dominant bacterial type. Resistance can be due to any number of mechanisms, including the appearance of lysogens or the selection for novel natural genetic variants.